High pressure arc cooled by a thin film of liquid on the wall of the envelope



EFEREEE 3mm WW1 Jan. 30, 1968 J. E. ANDERSON 3,366,815

' HIGH PRESSURE ARC COOLED BY A THIN FILM OF LIQUID ON THE WALL OF THE ENVELOPE Filed Dec. 29, 1965 INVENTOR. I JOHN E ANDERSON Q M A ORNEY United States Patent ABSTRACT OF THE DISCLOSURE An arc radiation torch having a high pressure are es tablished between two electrodes located adjacent the ends of the torch and forming an arc chamber therebetween and cooling means comprising means for bleeding at small quantity of liquid into the chamber, which liquid is spread.

as a thin film over the inner surface of the chamber for continuously cooling said chamber. The liquid is spread by gas which is in a swirling flow pattern such that it also constricts the arc.

This invention relates to an: radiation sources, and more particularly to a novel. method and means for cooling such sources.

The invention provides an arc radiation source comprising a transparent elongated envelope or tube; elec trodes located adjacent the ends of said envelope; means for energizing a high pressure are in said envelope be tween said electrodes, and cooling means comprising means for continuously bleeding liquid into said envelope in sufiicient quantity only to keep wet the inner surface of said envelope; and means for spreading such liquid only over such. inner surface in a thin film. while simultaneously constricting said are along lineal path between. the electrodes.

While prior radiation sources achieve a relatively long, high current. density are, they are not without their prob lems; the most serious problem 18 that of deterioration of the transparent envelope or tube forming the arc cham 'ber. Such deterioration is caused primarily by the heat generated by the are.

In. one method of attempting to solve the deterioration problem in prior arc radiation sources, a fluid such as water, was passed over and around the outer surface of the transparent tube. But such method does not directly remove the heat from. the inner surface where it; is being generated.

It is, therefore, the principal object of the present invention to provide an arc radiation source having a useful life that dramatically and far exceeds that of the prior art by virtue of superior cooling advantages.

In accordance with. the invention, there is provided a method of cooling an arc radiation source in which a lineal high pressure are is energized along the axis of a. transparent elongated envelope or tube, which comprises continuously spreading only a thin film of liquid over the inner surface of said. envelope. The thin film of liquid is formed over substantially the entire inner surface of the transparent envelope or tube by utilizing the swirling gas flow pattern of an arc constricting gas to force the liquid only over such inner surface. While distilled water the preferred liquid, other transparent liquids such as tap water may also be used,

As shown in the accompanying drawing in which the single figure is a view mainly 'n longitudinal cross section of an arc radiation source embodying the invention, a transparent tube or cylindrical envelope 10, composed of quartz, for example, is supported adjacent its ends in terminal members '12 and 14, respectively, composed of copper. Such members are hollow, their chambers 16 and 18 being continuous with the elongated chamber 20 of the tube 1.0..

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The members 12 and 14 are provided with electrodes 22 and 24 located concentrically with respect to the lon gitudinal axis of the tube 10 for carrying a lineal high pressure are when such electrodes are energized by connection to a suitable source of electric power (not shown).

The member 14 also is provided with gas inlet ports 26, as well as cooling liquid inlet ports 28 that extend between the inner wall 30 of chamber 18 and annular cooling water distribution manifold 32 and gas distribution manifold 34, respectively. The liquid inlet ports 28 are substantially equally spaced and their axes are arranged in frusto-conical surface of revolution that is concentric with the longitudinal axis of the arc chamber 20, being inclined so as to bleed cooling liquid into such chamber.

The gas inlet ports 26 are substantially equally spaced with their axes located in a plane that is perpendicular or transverse to the longitudinal axis of the chamber 20, which plane is positioned behind the liquid inlet ports 28. The axes of the gas inlet ports are tangent to a common circle that is concentric with such axis, so as to give the gas a swirling flow pattern. throughout. the chamber 20, which not only constricts the are, but also spreads the cooling liquid from the ports 28 in a thin film over substantially the entire inner surface of the tube The member 12 is provided with an annular outlet 36 for discharge of the gas and the liquid film from the arc chamber 20. The electrode 22 (anode) is cooled by circulating water through inlet and outlet passages 38 and 40. Similarly electrode 24 (cathode) is cooled by air culating water through inlet and outlet passages 42 and 44. The cathode 24 is insulated from. the rest of the as sembly by a ceramic or plastic sleeve 25, Body is located between members 12 and 14 and is provided with a high reflective inner surface 48 that is semi-elliptical, as shown; or completely elliptical as shown in the copending application of Anderson and Jackson, filed concurrently herewith, for Continuous Wave Lasers" .A suitable arc gas such as the inert. gases of argon xenon and krypton, is introduced into the arc chamber through the gas inlets so that the gas enters the chamber in a swirling fashion. These inert gases have a high atomic number which yields a high probability of elec tronic transition that is necessary for good radiation.Theswirling gas flows in such swirling fashion, near thearc along the axis of the chamber from whence it discharges. This flow pattern creates a lineal highly intense arc of high. current density.

An. important feature of this invention is that the arc gas is utilized to spread the thin film of liquid coolant over substantially the entire inner surface of the tube.-

The liquid, which may be tap water, or may be as preferred-distilled water, is allowed to seep /2 g.p.m.) into the arc chamber, so that the swirling gas readily spreads the liquid into a thin uniform film. Such uniformity is desirable to prevent distortion of the radiation rays.

Uniformity is also increased by proper selection of thenumber of ports, and by directing or slanting the ports toward the tube.

As an alternative to the use of. water, a liquid suitable for absorbing unwanted radiation rays may be used. For example, a sodium chromate or a sodium nitrate solution may be used to absorb ultraviolet rays.

In an experiment showing advantages of the invention, a radiation source of the type depicted was tested with and without the film of liquid (distilled water) being spread over the inner surface of the transparent tube. At. an electrical input of about 7.5 kw. a radiation output of. 409 watts (5.52%) was recovered in an ink-water-solw tion (for radiation measuring purposes) with water on. Without the water, an output of 464 watts was recovered. When. the water was turned. olf, the transparent. tube 3 sembly tailed. within 50 seconds. With the water, a run of about it) minutes was made, Howeverv the quartz; tube would last indefinitely. Thus at a small loss of radiation, the thin film. of water effectively cools the transparent: tube assembly, and substantially increases the useful life thereof What is claimed. is;

1 An arc radiation source comprising a transparent elongated. envelopev electrodes located adjacent the ends of said en elope for establishing a high pressure arc therebetween, and cooling means comprising means for con-- tinuously bleeding liquid into said envelope in sufiicient. quantity only to keep wet. the inner surface of said en velope, means for spreading such. liquid only cover such. inner surface in a thin film. while simultaneously constrict-- ing said arc along a lineal path between said electrodes and means for discharging said liquid from said envelope.

.2, An arcradiation source as defined by claim 1 eluding hollow means connected to one end of said envelope with the inner wall thereof :ontinuous with that of the envelope, said means being provided with liquid inlet: ports for bleeding the cooling liquid for such film toward such inner surface of the envelope, and with gas .inlet ports located behind such liquid inlet ports for directing are constricting gas in a swirling fiow pattern. while simultaneously spreading the liquid film. over substantially the entire inner surface of the envelope,

3. An arc radiation source as defined by claim 2, where In said discharge means is located at. the other end of said envelope, and is provided with an annular outlet. for the liquid of such. film as it leaves the inner surface oi; the envelope, as well. as for such a c constricting gas,

4. An art: radiation. source as defined h'y' claim. 2, in which such gas inlet: ports are substantially equally spaced.

and are arranged with their axes located in a common plane that is perpendicular to the longitudinal axis of the envelope, the axes of said ports being tangent to a common circle that is concentric with such longitudinal axis.

5: An arc radiation source as defined by claim 4, in which such liquid inlet ports are substantially equally spaced and are arranged with their axes located in a frusto conical. surface of revolution that is concentric with such longitudinal. axis,

6 Method of cooling an arc radiation source in which a lineal high pressure arc is energized along the axis of a transparent elongated envelope, which comprises: passing gas through the elongated envelope in a swirling flow pattern; and continuously introducing a relatively small. quantity of cooling liquid into said envelope in. the path of said swirling gas how such that said gas pro iects the liquid against the inner surface of said envelope while spreading said liquid in a thin film over substantially said entire inner surface,

7, Method as defined by claim 6, in which said liquid film. is substantially transparent, the envelope is composed of quartz, and the gas is selected from the class consisting or argon, xenon and krypton.

References Cited UNITED STATES PATENTS 2,906,858 9/1959 Morton 219-4121 3,082,314 3/1963 Arata et al -s 21975 3,149,222 9/1964 Gianinni et al M 219-121. 3,233,147 2/1966 Ducati 313-23]. X

JAMES W. LAWRENCE, Primary Examiner,

C1 R, CAMPBELL, Assistant Examinen 

